In a conventional cooling system for an internal combustion engine, the coolant is circulated by a circulating pump through the engine block, through the cylinder heads, eventually through the intake manifold. In an automobile, or other land vehicle, the coolant flows through a radiator. Most marine engines do not have a radiator. In a marine engine having an open loop cooling system, sea water supplied by a sea water pump is used to directly cool the engine and is then discharged overboard.
Other engines have closed loop cooling systems. In a closed loop cooling system, an engine coolant circulates through the engine and then through a heat exchanger.
In closed loop cooling systems, the flow of engine coolant through the heat exchanger is controlled by a thermostat on the engine block of the engine. When the engine and engine coolant are cold, the thermostat is closed so that coolant does not pass through the heat exchange. With the thermostat closed, a small portion of engine coolant flows through a bypass and returns a limited amount of coolant to the circulating pump, so that there is a sufficient engine coolant flow through the engine block while the system is warming up. While a limited amount of engine coolant is adequate when the engine warms up slowly, problems can occasionally exist if the operator runs the engine wide open before the engine and coolant have warmed up. Under these conditions, coolant flow through the engine bypass before the thermostat opens might not provide sufficient cooling. This can be critical because wide open operation can quickly to hot spots in the an engine. The present invention addresses such a need.